1. Field of the Invention
This invention relates to a package especially adapted for use with a dental appliance that is precoated with adhesive for direct bonding to tooth structure.
2. Description of the Related Art
Certain types of dental appliances are used with an adhesive for bonding the appliance to tooth structure. For example, orthodontic brackets typically have a base surface that is "buttered" or coated with an adhesive for bonding to a labial or lingual surface of the tooth. Such brackets are used in orthodontic treatment to serve as a handle for the tooth so that the tooth can be moved to a desired position.
Examples of recent advances in the field of direct bonded dental appliances are described in U.S. Pat. Nos. 4,978,007, 5,015,180, 5,172,809 and 5,348,154, all of which are assigned to the assignee of the present invention. U.S. Pat. No. 5,015,180 describes in one embodiment an orthodontic bracket and a light curable paste sandwiched between a base of the bracket and a flexible, releasably adhering cover sheet. To bond the bracket to a tooth, the cover sheet is removed from the paste and the bracket base is then applied to the tooth. The invention described in U.S. Pat. No. 5,015,180 represents a time savings for the orthodontic practitioner because the adhesive can be coated onto the bracket base by the manufacturer, and the practitioner need not carefully dispense and apply the adhesive to the bracket base before bonding the bracket to the tooth.
U.S. Pat. Nos. 4,978,007, 5,172,809 and 5,348,154 describe in one embodiment a container or substrate having a recess, an orthodontic bracket having an adhesive on an exterior surface, and a cover extending over the recess. Such construction is advantageous in that the adhesive in the recess is protected from light, oxygen, water vapor and contaminants. Preferably, the bracket is retained in the recess in an orientation that facilitates grasping of the bracket for direct placement onto the tooth surface.
Orthodontic brackets are available in a wide variety of configurations or prescriptions. For example, the base of the bracket may have a particular configuration that matches the contour and size of a particular tooth. In addition, the number and shape of the tiewings, the shape and size of the archwire slot, and the characteristics of other elements of the bracket may vary in accordance with the needs of the patient and the treatment technique preferred by the orthodontist. Moreover, certain specialized brackets, such as brackets with hooks or other auxiliary attachments, may be desirable in some instances. As a consequence, the orthodontist may choose to retain a wide variety of brackets on hand so that the desired brackets can be immediately selected and put into use without waiting for additional brackets to be shipped from the manufacturer.
As can be appreciated, some precoated orthodontic brackets that are ordered from the manufacturer by the orthodontist for the orthodontist's own inventory may not be used for some time after manufacture. For this reason, efforts have been made in the past to ensure that the adhesive retains its expected bonding and handling characteristics in reliable fashion over the expected shelf life of the packaged bracket. Shelf life issues relating to the adhesive are important, because an adhesive that does not properly bond the bracket to the tooth may subsequently debond in spontaneous fashion. Such an occurrence is a nuisance to both the patient and the orthodontist, since the patient must return to the orthodontist for rebonding or replacement of the bracket.
Examples of packages for adhesive precoated dental appliances such as orthodontic brackets are described in U.S. Pat. Nos. 5,328,363 and 5,350,059. Such packages include a container having a well to receive the appliance. The container includes a top flange surrounding an opening over the well, and a cover extends over the opening and the flange to initially close the well. Preferably, each appliance is individually packaged, so that certain brackets as may be needed for a particular patient can be selected, arranged in a set-up tray and carried to the patient's chair in convenient fashion. Individual packaging also helps insure that the appliance and the adhesive are not unduly exposed to the atmosphere before use.
The container and the cover for the packaged dental appliance as described in U.S. Pat. Nos. 5,328,363 and 5,350,059 are each made from a sheet of flexible material that provides a substantial barrier to the transmission of oxygen, water vapor and light having a wavelength that might otherwise cause the dental adhesive to prematurely cure. A pressure sensitive adhesive is provided to join the cover to the flange. Optionally, a repositionable adhesive can be used to enable the orthodontist to reclose the package as may be desired in certain instances.
There is a continuing need in the art to improve the shelf life of packaged, adhesive precoated dental appliances such as orthodontic brackets so that the brackets can be retained in the orthodontist's inventory for longer periods of time without adversely affecting the handling or bonding characteristics of the adhesive. Preferably, any such improvements should not add significant additional expense, should be reliable in use, and should not render the package difficult to open.